Embodiments of the present disclosure relate to power plants, and more particularly to combined power plants.
Conventionally, a power plant converts latent energy of a substance into electric power. For example, a steam turbine power plant converts the latent energy of high-pressure steam into electric power. To this end, the steam turbine power plant includes multiple stages of interspersed stationary nozzles and rotating blades. When steam is introduced into the turbine, the stationary nozzles direct the steam towards the rotating blades. The force with which the steam impinges on the rotating blades forces the blades to rotate at a speed corresponding to the potential and kinetic energy of the steam. The mechanical energy of the rotating blades is converted into electric power using an electric generator.
In typical steam turbines, exhaust steam is generally released into the environment. In the last few decades, however, to control the increasing expenses of operating a steam turbine power plant, engineers have attempted to increase the efficiency of the power plant. One such power plant is a reheat power plant. In this power plant, the steam released by the steam turbine is condensed and reheated for further utilization by the steam turbine. Subsequently, combined-cycle power plants were devised to further increase power plant efficiency. In these power plants, two or more power plants are combined such that the combined efficiency of the power plants is greater than the efficiency of the individual power plants. For example, in a gas-steam combined-cycle power plant, hot gases expelled by a gas turbine are utilized to generate steam for the steam turbine, thereby increasing the overall efficiency of the power plant. Along a similar principle, power plants in which the exhaust steam from a high-pressure steam turbine is further utilized by a low-pressure steam turbine were developed. Recently, supercritical steam turbines and ultra-supercritical steam turbines have been developed that can handle steam having very high temperature and/or pressure, thereby enhancing plant efficiency.
Although these modifications to the power plants increase efficiency, some of these modifications may require design changes in the existing steam turbine plants. Such modifications can be very expensive to implement. Moreover, other alterations to the power plants may only marginally increase their efficiency.